1. Field of the Invention
2. Prior Art
The invention relates to an artificial heart capable of being wholly implanted.
Document EP-A-0 079 373 discloses a complete cardiac prosthesis whose ventricular chambers are actuated by pumps separate from the heart itself. This results in substantial load losses, a large volume of pumping oil and a certain bulkiness of the system.
A significant improvement has been obtained by virtue of the architecture described in document FR-A-2 625 903. This architecture, which is the basis of the present invention, is characterized by a one-piece module housing two independent ventricular chambers each provided with two orifices fitted with valves respectively for the expulsion and admission of blood, each chamber having a variable volume by virtue of a movable membrane which forms a wall of the chamber and is hydraulically operated by a fluid driven by an actuator comprising a motor and a volumetric pump integrated within the body.
In the artificial heart described in the above documentxe2x80x94just as in the one described in EP-A-0 079 373xe2x80x94the ventricular chambers are face to face forming a V-shape with the point at the bottom, and between the branches of which are arranged the expulsion and admission orifices for attachment to the natural organs. The exterior of the V is reserved for the hydraulic chambers that actuate the membranes and for the motorized pumps, in an appendicular position.
U.S. Pat. No. 4,750,903 states that it is not possible to miniaturize a membrane type of heart sufficiently to make it truly implantable and proposes a different, pocket-type heart.
In spite of its interest, this artificial heart can still be improved both from the point of view of compactness and also by the reduction of hydraulic pressure losses on the actuating side. Such is the object of the present invention.
The present invention distinguishes from the above by an architecture which runs counter to the orthodox approaches. It is essentially characterized in that the ventricular chambers are arranged so as to form an upside down V, i.e. with the point at the top, and between the branches of which are arranged the above-mentioned actuators and the space intended for the actuating fluid.
Thanks to this revolutionary architecture, the heart""s overall volume can be reduced by obviating the need for a collector which, in the previous architecture, has to pass round the connector flange between the ventricular chamber and the actuating chamber to bring the actuating fluid thereto. In the proposed new architecture, the positions of the ventricular and actuating chambers have been exchanged, the centrally mounted actuators expulse the fluid directly into the actuating chambers; load losses are reduced, and the total quantity of actuating fluid required is lower and easy to confine to the center of the heart. Moreover, by contrast with the known architecture, it is no longer necessary to provide a protective strainer for the supple reservoir bag which encloses the operating oil and which was up till now provided to prevent an untimely aspiration of the bag by the pumps.
Another advantage of the new heart is that all the surfaces in contact with blood can easily be made hemocompatible; indeed, apart from the hemocompatible membrane known in the state of the art, all the other surfaces intended to be in contact with blood are advantageously made of titanium, well known for its excellent hemocompatibility.
The ventricular chambers of the wholly implantable heart according to the invention externally present curved walls on which are arranged the expulsion and admission orifices.
According to a very advantageous characteristic of the invention, the actuators are arranged substantially within the zone of the median symmetry plane of the V formed by the chambers, their axes approximately forming a right angle, the motors being located outside the right angle and the pumps inside the right angle.
According to the invention, the artificial heart comprises a central body which provides one or a plurality of the following functions:
left and right ventricles containing the membrane actuating fluid
actuating fluid reservoir
support and positioning for the actuator motor pump units
pump fluid collector
pump distributor
membrane mount
pressure and position sensor mount
mount for fixing and sealing the supple bag fluid reservoir
electronic circuit board mount for the motor drive circuit, sensor conditioning electronics and medical control and regulation electronics
mount for the external connection electrical cord
mount for the ventricular caps and the external body shell.
Advantageously, the central bodyxe2x80x94which is preferably made of plastics materialxe2x80x94supports the actuators and defines two cups inclined to form a V-shape, the rim of which retains the movable membrane surmounted by the above-mentioned curved wall made of titanium, each cup forming with the membrane an actuating chamber supplied with oil by the actuators, whose pump is interposed between the internal space of the above chamber and an oil confinement space formed in and around the central body and limited by a supple bag reservoir, the entire assembly being enclosed in a rigid titanium body shell.
The central portion fitted with the actuating units, sensors, membranes and the electronics immerged in the fluid confined in a supple reservoir forms an autonomous and intelligent actuating system.
The biological part, formed by a shell and two ventricular caps with the connection pipes supporting the valves, completely surrounds the actuator and is made of microballed titanium sheeting to ensure compatibility with blood and tissues.
Some of the characteristics and advantages described in document FR-A-2 625 903 are or can be adopted in the novel architecture of the invention:
separation of the blood zones and zones serving for actuation and regulation
electrohydraulic actuation provided by a brushless direct current motor and a volumetric pump with internal gears and radial expulsion
use of a complex membrane ensuring compatibility with blood and the actuating fluid
independent flowrates for the right and left ventricles
connection between the prosthesis and the auricles by a spectacle-shaped quick connector
hemocompatibility and biocompatibility ensured by porous surfaces made of biocompatible materials
flowrate regulation through speed variation of the electric motors controlled by a digital electronic system reproducing in real time the behavior of the cardiac muscle from measurements of the ventricular pressure and volumes expulsed by the volumetric pumps.